Tid Bits. How you can be distorying your good running engine

[Bob Dunahugh]

And you will never know it till it's TOO LATE. Your 403, or 455 came with a=
cam gear that had an aluminum gear sprocket center. That has a plastic ge=
ar around it. Most of us are concerned about the cam chain getting loose. T=
hus retarding the cam shaft timing. That WILL NOT destroy your engine. But =
when the plastic/aluminum cam gear plastic starts to break off the aluminum=
core. Next the steel chain starts chewing up the aluminum sprocket core. T=
his then can produce lots of plastic/ aluminum contamination that then rest=
ricts ( plugs up ) the oil flow of your oil filter. Then all that contamina=
tion causes the oil filter bypass valve to open. So since the oil filter c=
an't filter the oil anymore. Then this contamination starts to destroy your=
engine main/rod bearings. The replacement chain/sprocket sets are all stee=
l. So if your engine is running great. And has never been rebuilt. You ARE =
on barrowed time. PIROID. So a couple of hundred to replace the chain set.=
Or a few thousand for a complete rebuild. This well happen at some point.=
When we bought or first 78 Royale in 2003. One of the first things I did w=
as to change that chain set. Our origin cam sprocket was still fine. That 4=
03 still runs great at 154,000 miles. Simple choice. Bob Dunahugh

 

[bdub1]

And what causes this?

Piroid

-----Original Message-----
From: Gmclist On Behalf Of Bob Dunahugh
Sent: Tuesday, May 1, 2018 8:21 AM
Subject: [GMCnet] Tid Bits. How you can be distorying your good running
engine

... snip ... "But when the plastic/aluminum cam gear plastic starts to break
off the aluminum core. "

 

[Carl Stouffer]

I think it is caused mostly by age, fatigue, heat cycles, etc. rather than mileage, Billy
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[Bob Dunahugh]

I have a small inspection camera. Pulling the fuel pump should get a view o=
f the came gear in that manner Bob Dunahugh. _____________________=
___________ From: Bob Dunahugh Sent: Tuesday, May 1, 2018 8:21 AM To:=
gmclist Subject: Tid Bits. How you can be distorying you=
r good running engine And you will never know it till it's TOO LATE. Y=
our 403, or 455 came with a cam gear that had an aluminum gear sprocket cen=
ter. That has a plastic gear around it. Most of us are concerned about the=
cam chain getting loose. Thus retarding the cam shaft timing. That WILL NO=
T destroy your engine. But when the plastic/aluminum cam gear plastic start=
s to break off the aluminum core. Next the steel chain starts chewing up th=
e aluminum sprocket core. This then can produce lots of plastic/ aluminum c=
ontamination that then restricts ( plugs up ) the oil flow of your oil filt=
er. Then all that contamination causes the oil filter bypass valve to open=
. So since the oil filter can't filter the oil anymore. Then this contamina=
tion starts to destroy your engine main/rod bearings. The replacement chain=
/sprocket sets are all steel. So if your engine is running great. And has n=
ever been rebuilt. You ARE on barrowed time. PIROID. So a couple of hundre=
d to replace the chain set. Or a few thousand for a complete rebuild. This=
well happen at some point. When we bought or first 78 Royale in 2003. One =
of the first things I did was to change that chain set. Our origin cam spro=
cket was still fine. That 403 still runs great at 154,000 miles. Simple ch=
oice. Bob Dunahugh

 

[Jim Hupy]

Not all of the 455/403 engines have the cylent timing set. In fact, the
agricultural engines were not factory fitted with them. That is not to say
that you will NEVER ENCOUNTER one in a GMC. 40 years is a long time, and a
whole bunch of stuff can happen in those passing years. If your engine is
fitted with them, best advise would be to remove and replace them with a
true roller set.
Jim Hupy

> I have a small inspection camera. Pulling the fuel pump should get a view
> of the came gear in that manner Bob Dunahugh.
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Tuesday, May 1, 2018 8:21 AM
> To: gmclist
> Subject: Tid Bits. How you can be distorying your good running engine
>
> And you will never know it till it's TOO LATE. Your 403, or 455 came with
> a cam gear that had an aluminum gear sprocket center. That has a plastic
> gear around it. Most of us are concerned about the cam chain getting loose.
> Thus retarding the cam shaft timing. That WILL NOT destroy your engine. But
> when the plastic/aluminum cam gear plastic starts to break off the aluminum
> core. Next the steel chain starts chewing up the aluminum sprocket core.
> This then can produce lots of plastic/ aluminum contamination that then
> restricts ( plugs up ) the oil flow of your oil filter. Then all that
> contamination causes the oil filter bypass valve to open. So since the oil
> filter can't filter the oil anymore. Then this contamination starts to
> destroy your engine main/rod bearings. The replacement chain/sprocket sets
> are all steel. So if your engine is running great. And has never been
> rebuilt. You ARE on barrowed time. PIROID. So a couple of hundred to
> replace the chain set. Or a few thousand for a complete rebuild. This well
> happen at some point. When we bought or first 78 Royale in 2003. One of the
> first things I did was to change that chain set. Our origin cam sprocket
> was still fine. That 403 still runs great at 154,000 miles. Simple
> choice. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Bob Dunahugh]

Carl S. I agree with your reasons 100%. I've seen this from high, and low =
mileage engine that had those gears. I bought a 403 to keep around as a cor=
e. Had been rebuilt. And had that the plastic/aluminum gear installed. Ran =
well. When it was disassembled. A third of the plastic gear was gone to the=
bottom of the oil pan. Found plastic shavings embedded in the rod/main bea=
rings. Bob Dunahugh ________________________________ From: Bob =
Dunahugh Sent: Tuesday, May 1, 2018 7:13 PM To: =
gmclist Subject: RE: Tid Bits. How you can be distorying =
your good running engine I have a small inspection camera. Pulling =
the fuel pump should get a view of the came gear in that manner Bob Dunahu=
gh. ________________________________ From: Bob Dunahugh Sent: T=
uesday, May 1, 2018 8:21 AM To: gmclist Subject: Tid Bi=
ts. How you can be distorying your good running engine And you will ne=
ver know it till it's TOO LATE. Your 403, or 455 came with a cam gear that =
had an aluminum gear sprocket center. That has a plastic gear around it. M=
ost of us are concerned about the cam chain getting loose. Thus retarding t=
he cam shaft timing. That WILL NOT destroy your engine. But when the plasti=
c/aluminum cam gear plastic starts to break off the aluminum core. Next the=
steel chain starts chewing up the aluminum sprocket core. This then can pr=
oduce lots of plastic/ aluminum contamination that then restricts ( plugs u=
p ) the oil flow of your oil filter. Then all that contamination causes th=
e oil filter bypass valve to open. So since the oil filter can't filter the=
oil anymore. Then this contamination starts to destroy your engine main/ro=
d bearings. The replacement chain/sprocket sets are all steel. So if your e=
ngine is running great. And has never been rebuilt. You ARE on barrowed tim=
e. PIROID. So a couple of hundred to replace the chain set. Or a few thous=
and for a complete rebuild. This well happen at some point. When we bought=
or first 78 Royale in 2003. One of the first things I did was to change th=
at chain set. Our origin cam sprocket was still fine. That 403 still runs g=
reat at 154,000 miles. Simple choice. Bob Dunahugh

 

[bdub]

I changed mine out @ 85,000 miles as advised on this list. The chain was
streched. Still truckin 55k miles down the road.
bdub

>
>

Carl S. I agree with your reasons 100%. I've seen this from high, and low
mileage engine that had those gears. I bought a 403 to keep around as a
core. Had been rebuilt. And had that the plastic/aluminum gear installed.
Ran well. When it was disassembled. A third of the plastic gear was gone to
the bottom of the oil pan. Found plastic shavings embedded in the rod/main
bearings. Bob Dunahugh

________________________________
From: Bob Dunahugh
Sent: Tuesday, May 1, 2018 7:13 PM
To: gmclist
Subject: RE: Tid Bits. How you can be distorying your good running engine

I have a small inspection camera. Pulling the fuel pump should get a view
of the came gear in that manner Bob Dunahugh.

________________________________
From: Bob Dunahugh
Sent: Tuesday, May 1, 2018 8:21 AM
To: gmclist
Subject: Tid Bits. How you can be distorying your good running engine

And you will never know it till it's TOO LATE. Your 403, or 455 came with a
cam gear that had an aluminum gear sprocket center. That has a plastic
gear around it. Most of us are concerned about the cam chain getting loose.
Thus retarding the cam shaft timing. That WILL NOT destroy your engine. But
when the plastic/aluminum cam gear plastic starts to break off the aluminum
core. Next the steel chain starts chewing up the aluminum sprocket core.
This then can produce lots of plastic/ aluminum contamination that then
restricts ( plugs up ) the oil flow of your oil filter. Then all that
contamination causes the oil filter bypass valve to open. So since the oil
filter can't filter the oil anymore. Then this contamination starts to
destroy your engine main/rod bearings. The replacement chain/sprocket sets
are all steel. So if your engine is running great. And has never been
rebuilt. You ARE on barrowed time. PIROID. So a couple of hundred to
replace the chain set. Or a few thousand for a complete rebuild. This well
happen at some point. When we bought or first 78 Royale in 2003. One of the
first things I did was to change that chain set. Our origin cam sprocket
was still fine. That 403 still runs great at 154,000 miles. Simple
choice. Bob Dunahugh
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[Bruce Hart]

Worked on installing axels this past week and had a bad thread in the
rotating flange on final drive. Couldn't use a tap handle as the shift
linkage from the tranny was in the way. Found a nut (3/8-16) and pressed
it on (bench vice) the square end of tap and used a ratcheting socket
wrench to clean out the tread.

> I changed mine out @ 85,000 miles as advised on this list. The chain was
> streched. Still truckin 55k miles down the road.
> bdub
>
>
>
> >
> >

>
> Carl S. I agree with your reasons 100%. I've seen this from high, and low
> mileage engine that had those gears. I bought a 403 to keep around as a
> core. Had been rebuilt. And had that the plastic/aluminum gear installed.
> Ran well. When it was disassembled. A third of the plastic gear was gone to
> the bottom of the oil pan. Found plastic shavings embedded in the rod/main
> bearings. Bob Dunahugh
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Tuesday, May 1, 2018 7:13 PM
> To: gmclist
> Subject: RE: Tid Bits. How you can be distorying your good running engine
>
>
>
> I have a small inspection camera. Pulling the fuel pump should get a view
> of the came gear in that manner Bob Dunahugh.
>
>
> ________________________________
> From: Bob Dunahugh
> Sent: Tuesday, May 1, 2018 8:21 AM
> To: gmclist
> Subject: Tid Bits. How you can be distorying your good running engine
>
> And you will never know it till it's TOO LATE. Your 403, or 455 came with a
> cam gear that had an aluminum gear sprocket center. That has a plastic
> gear around it. Most of us are concerned about the cam chain getting loose.
> Thus retarding the cam shaft timing. That WILL NOT destroy your engine. But
> when the plastic/aluminum cam gear plastic starts to break off the aluminum
> core. Next the steel chain starts chewing up the aluminum sprocket core.
> This then can produce lots of plastic/ aluminum contamination that then
> restricts ( plugs up ) the oil flow of your oil filter. Then all that
> contamination causes the oil filter bypass valve to open. So since the oil
> filter can't filter the oil anymore. Then this contamination starts to
> destroy your engine main/rod bearings. The replacement chain/sprocket sets
> are all steel. So if your engine is running great. And has never been
> rebuilt. You ARE on barrowed time. PIROID. So a couple of hundred to
> replace the chain set. Or a few thousand for a complete rebuild. This well
> happen at some point. When we bought or first 78 Royale in 2003. One of the
> first things I did was to change that chain set. Our origin cam sprocket
> was still fine. That 403 still runs great at 154,000 miles. Simple
> choice. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class